The European Union has undertaken to reduce its emissions of greenhouse gases by 20 per cent by the year 2020. Within the EU around 160 million buildings account for 40 per cent of primary energy consumption and a considerable proportion of CO2 emissions. Most of that energy is used for space heating (in private households around 76 per cent). Buildings therefore offer tremendous potential for saving energy and reducing CO2 emissions.The Energy Performance of Buildings Directive (EPBD), which came into force in 2002, puts the onus for action on the individual member states. In Germany the EPBD prompted a revision of the existing Energieeinsparverordnung (Energy Conservation Regulations), or EnEV. EnEV 2007 made it obligatory for buildings to have energy certificates – a voluntary system had been in operation since 1989.